Its a good thing the Duke was a mage huh?
I was wondering when the Duke had time to change out of his night clothes and into his robes.
The duke is an elf sorceror, not a wizard. The characters have known the duke to be such an individual since episode 1 (the episode about which we are talking was episode 41 of the campaign). The sorceror in the party did not choose this NPC out of the blue; he chose him because he was the highest-level spellcaster in the vicinity of the combat.
As far as I understand elves, they don't sleep. As far as I understand sorcerors, their big mechanical advantage is that they're almost always equally prepared. (Case in point, the sorceror who sought the duke's aid.)
One last thing: people are suggesting that I enforced the armour donning rules because they reflected reality. Bzzt. Wrong. I enforced them because they were specifically codified rules in the book. If there is no rule on point, I make a judgement call. If, however, there is a rule in the books that specifically speaks to a situtation, whether it makes sense or not, I enforce the rule. In my view, a game in which the players do not know, from minute to minute, which rules are really in effect is an unfair game in which people cannot make reasonable tactical decisions because the goal posts are constantly shifting.
So, to reiterate, if the rules are silent on something, I make a judgement call about it, which is almost always favourable to the players gut if the rules directly speak to something, unless there is a known, agreed-upon house rule, the rules, as articulated in the books are in effect.
While I can understand the viewpoint of some, like Tsyr, who have a stylistic disagreement with me setting up the encounter the way I did, I really have no sympathy for those who argue that the DM should be able to, arbitrarily and without notice, decide which rules should be in force when.
Some people have also stated that they think heavy armour is a bad thing because you cannot sleep in it and it slows you down. Fair enough, I guess but it was my players' decision, not mine, to make it their primary armour.